Manufacture of fuel gas



Dec. 22, 1931. H. o. LOEBELL 1 1,837,226

MANUFACTURE OF FUEL GAS r Filed May 23, 1923 2 Sheets-Sheet 1 Del 22il931. H. c LOEBELL 1,337,226

MANUFACTURE OF FUEL GAS Filed May 23, 192:5 2 Sheets-Sheet 2 PatentedDec. 22, 1931 ATENT OFFICE HENRY O. LOEBELL, 01' NEW YORK,

N. Y ASSIGNOB TO HENRY L. DOHERTY, 01 NEW YORK, N. Y.

MANUFACTURE OF FUEL GAS Application filed Kay 23, 1923. Serial No.640,828.

This invention relates to the manufacture of fuel gas, and moreparticularlyto a meth- 0d of making gas for industrial purposes by thecomplete gasification of coal.

The gas which is now being commonly burned for industrial heatingpurposes is known asa producer gas which has a com-- paratively lowcalorific value. This gas is manufactured by a process of burning coalwherein inert gases such as nitrogen-of the air used and carbon dioxideformed by combustion of carbon with the air remain in the gas so that55% to 65% of thejgas is formed of inert constituents. Producer. gas hasa limited use for industrial heating purposes, because it has a lowflame temperature, a low calorific value and a slow flame propagation.Some heating processes require comparatively high flame temperatures andan attempt has been made to make a blue water gas for this purpose. The.so called blue water gas has a comparatively high flame temperature anda comparatively low percentage of inert constituents, but the cost tomanufacture blue water gas isvery high and the yield of the blue watergas from a ton of coal is comparatively small as compared with theamount of producer gas which can be made from a ton of coal.

One object of the present invention is to provide a method ofmanufacturing an industrial fuel gas which has a comparatively highflame temperature, a rapid flame propagation, and a calorific valuewhich adapts it for practically all industrial heating purposes. p I

Another object of the invention is to provide a method of makingindustrial gas by which valuable by-products may be recovered and atthesame time a gas will be .produced which is free of contaminating andeleterious constituents.

A further object of the invention is to provide a process of makingindustrial gas which is efficient, in the conservation of heat and whichmay be completely controlled to control the character of gas being made.

lVith these and other objects and features in view, the inventionconsists in-the improved gas making process hereinafter dethereof. Theportion of t scribed and specifically defined in the claims.

The various features of the invention are illustrated in theaccompanying drawings, in which r Fig. 1 is a view in vertical sectionwith parts in elevationof a gas generator embodyin the preferred form ofthe invention;

ig. 2 is a top plan viewof the generator shown in Fig. 1;

Fig.. 3 is a vertical sectional view of the waste heat boiler used withthe generator, the section being taken on the line 3'-3 of Fig. 2;

Fig. 4 is a horizontal sectional view taken on-the line 4-4 of Fig. 5,illustrating the mechanism for removing coke. from the bottom of thegenerator; and

Fi 5 is a vertical sectional view taken on the llne 5-5 of Fig. 4 toillustrate the coke discharging mechanism.

The method of making fuel gas embodying the preferred form of theinvention may be carried out in the apparatus illustrated in thedrawings substantially as follows:

Fuel to'be carbonized, which is preferably a cokin grade of bituminouscoal in mixture with co e, isplaced in a hopper 10 and is intermittentlylntroduced into the upper part of a generator shaft 12 by means of apocket the pocket 14 will be filled with coal. At

this timethe valve 18 is closed. Thereupon the valve- 16 will be closedand the valve 18 will be opened to allow the fuel to pass into the topof the generator shaft. The fuel discharging from the pocket 14 passesaround a central gas oif-take 20 and is distributed into the top of anupright column of fuel supported in the shaft 12. The upper portion ofthe fuel column or approximately the portion above the lower end ofthegas off-take 20, comprises a coal carbonizing zone. The portion ofthefuel column below the bottom of the ofi-take 20 and extending downwardlya short distance below an offset portion 22 in the shaft 12 constitutesa blast zone in which the fuel is maintained at a comparatively hightemperature by artial combustion lie fuel column from the bottom of theblast zone to the bottom of the column is a cooling or quenching zone inwhich the unburned carbonized fuel and ashes are quenched before beingremoved from the shaft. The unburned carbonized fuel is continuouslydischarged from the bottom of the column and continuously movesdownwardly through the shaft.

The gas is made by several distinct reactions which take place betweenthe fuel and the air and steam used for making the gas. The firstreaction is an exothermic reaction which takes place when air is used toburn carbon of the fuel, according to the following equation:

C+O +3.78 N

CO 3.78 N, 14600 B. T. U.

A second reaction takes place between the carbon of thev fuel bed andthe carbon dioxide which is formed by the combustion of air, inaccordance with the following equation, which is endothermic:

A third reaction takes place between carbon of the fuel bed and steamwhich is introduced at the fuel bed, the'reaction being endothermic, asfollows:

A fourth reaction is that which takes place when the volatile material,principally hydrocarbons, is distilled from the coal by the passage ofhot gases through the fuel column.

In the present process the air and steam used in making gas arepreheated and then introduced into the blast zone of the fuel column tocarry on reactions outlined above. The mixture of air and steam isheated in a pair of preheaters which are so arranged that one preheateris used for preheating the mixture, while the other preheater is beingheated by burning gas therein. When one preheater has been cooled to theminimum working temperature which is desirable, by passing steam and airthrough it, the circulation of the steam and air mixture is stopped andthen started in the other preheater which was be ing heatedduring thetime when the first preheater was used for heating the mixture of steamand air. To accomplish this air is introduced into. one of thepreheaters 24 through a pipe 26, and steam is supplied to the pipe 26through a pipe 28. The steam and air mixture enters the top of anexhaust section 30 of the preheater, passes downward- 1y through achecker brick filling in the sectlon 30, then through an openin 32 intothe bottom of the main section of the preheater 24, and thence passesupwardly through a checker brick filling in the main section. In passingthrough the two'sections of the preeater the steam and air mixturebecomes highly heated and it then flows through 3.

blast neck 34 into a passage 36 surrounding.

above, and the hot gas formed passes upwardly through the off-take incontact with a series of superheating tubes 38, wherein water vapor orsteam to be used for the gas making operation is superheated before itis introduced through the pipes 28 into sections 30 of preheaters 24.After passing through the off-take'20 the gas flows through outlets 40,Figs. 1 and 2, to a conduit 42 which conducts it to inlet flues 44 ofwaste heat boilers 46 and 48. In the waste heat boilers the hot gaspasses upwardly through a series of tubes 50, Fig. 3, to a passage 52 atthe top of the boiler, then downwardly through tubes 54 to an outletflue 56, whence the gas passes through a conduit 58 to a cooler ofsuitable construction, whereby the gas may be cooled and be ready topass to the place of consumption or to the usual holder (not shown).

In normal operation of the gas generator the hot gas carried off throughthe off-take 20 is used to heat the boilers 46. and 48 simultaneously.If, however, one of the boilers needs to be-cleaned or if one of theboilers gets out of order, all of the gas may be passed through one ofthe boilers at a time. To accomplish this a valve 60, Fig. 1, is mountedin the inlet fiue44 in a position to be moved into a, valve seat 62positioned at the bottom of the conduit 42. The valve is mounted upon arod 64 which moves through a stuffing box 66 positioned in the floor ofthe flue 44. To reciprocate the rod-64 through the stuffing box a chain68 is attached to the floor of the fine 44 and passes over pulleys 72and 74, down to an operating platform.

When the preheater 24, for example, shown at the left of Fig. 1, is usedfor preheating the air and steam mixture, the preheater 24, shown at theright, is being heated by burning gas therein. At this time thepreheater 24 at the right of Fig. 1 is cut off from the shaft 12 bymeans of a valve 76, and a portion of the 'gas from the conduit 58 isconducted through a pipe 78 and valve 80 into the top of the mainsection of the preheater. At the same time air is introduced through aninlet 82, and the mixture of burning gas and air passes downwardlythrough the main section of the preheater, then up wardly through theexhaust section 30 of the preheater, and exhausts through an outlet 84.A cover 86 on the outlet 84 is open during the heating operation of thepreheater, and the air and steam inlet pipes 26 and 28 are closedrespectively by suitable valves 85 and 87 (Fig. 1).

The central off-take 20 is supported on the top of the shaft 12 by theoutlet pipe 40 and also by a series of braces 88 whlchare attached tothe frame 90 of the generator.

The inner lining of the off-take consists of the superheating tubes 38which are connected between an inlet manifold 92 at the top, Figs. 1 and2, a distributing manifold 94 at the bottom, and an outlet manifold 96at the top. The steam to be superheated is introduced into the inletmanifold 92 by means of a pipe 95 which connects with a steam header 97,mounted between the waste heat boilers 46 and 48. Suitable valves 98 and100 are placed in the header 97 to control the flow of steam from theboilers. The steam flows from the inlet header 92 downwardly throughtubes 38 to the header 94 and then upwardly through tubes to the header96 and out through a pipe 102, which preferably is connected with thepipes 28 that enter the preheaters 24. Water is introduced into thewaste heat boilers'through inlet pipes 104. The waste heat boilers willabstract the larger portion of the heat from the fuel gas and this heatwill normally produce asuflicient amount of steam to take care ,of therequirements of the gas making operation. However, the waste heatboilers may be supplemented with other steam boilers in making up the.required amount of steam, so that one of the waste heat boilers may beshut down for any desired purpose.

By the time the fuel has moved downwardly through the carbonizing zoneand reached ,the blast zone there is substantially no volatile materialtherein and therefore the gas which passes upwardly through the.

offtake 20 contains substantially no tar, ammonia. or other productswhich, are usually formed in coal gas. Accordingly, the gas which leavesthe waste heat boilers does not require any special purification.

The volatile material of the coal and other valuable by-products such astars, oils and ammonia are removed from the coal by low temperaturecarbonization. To accomplish this, a small portion of the hot producergas being made inthe blast zone is led upwardly around the off-take 20through the carbonizing zone ofthe fuel column to slowly distill off theby-products. This small amount of 1 gas containing the by-productspassescinto an' outlet 106 at the top of the shaft, and flows through aconduit 108 which conducts it to the usual purification and treatingequipment (not shown). In this equipment the valuable by-products areremoved and the purified gas may then be mixed with the gas passingthrough the outlet pipe 58. By this means substantially all of. thevaluable byproducts of the coal may be continuously removed and the coalconverted into a coke or carbonized fuel which-is very well suited for ablue water gas reaction. The gas containing the by-products iscomparatively small in volume, compared with the entire'gas output ofthe producer, and therefore the by-products may be recovered by treatinga comparatively small amount of gas.

Although-the temperatures usedin the blast zone for making gas arecomparatively high, these temperatures are not sufliciently high to slagor clinker the fuel, and therefore a comparatively large amount of theunburned fuel passes down to the bottom of the fuel column. This fuel isprincipally coke or carbonized fuel and must be quenched to preventdestruction of the bottom of the shaft 12. To this end the unburnedcarbonized fuel and ash is supported in the bottom of the shaft upon aseries of hoppers 110, Figs. 1, 4, and 5. The hoppers are preferably.made of a steel construction and are protected by refractory masonarylining. The hoppers,-seven in number, consist of six peripheral hoppers,and a central hopper. An opening 112 is formed in the ing through theseopenings flows upon a series of movable platforms 116, which are spacedfrom, but directly under the openings; The platforms 116 are arranged tobe given a reciprocating motion by means of water operated engines 118to discharge the carbonized fuel from the platforms into .a hopper 120immediately below the hopper 110. To cool the carbonized fuel passingdown to the hopper 110 a water or steam pipe 122 is positioned below thehopper and has an outlet 124 extending into each of the open-' ing's 112and 114 by which water or steam may be directed into the carbonized fuelto quench and cool it. The water or steam introduced into the hotcarbonized fuel passes upwardly through the fuel column in the formof'vapor, thus acting to effectively cool the carbonized fuel in itsupward passage. By the time the steam reaches the blast zone it ishighly preheated and enters into reaction with the carbonized fuel ofthe fuel column, so that it isutilized in making gas in the same waythat the steam entering the fuel column through the preheater is used.

The carbonized fuel discharged from the hopper 110 to the hopper 120passes through a series of outlets 126 on the bottom of the hopper 120and is collected in a'chamber 128 at the bottom of the shaft.Periodically a door 130' at the bottom of the chamber 128 is opened andthe carbonized fuel accumulated therein may be drawn out. At the timethe a moved into position to cover the outlets 126 by means of operatingshafts 134. that extend to the outside of the shaft 12. When the door130 is closed the doors 132 are ened to permit the carbonized fuel topass rom the hopper 120 to the chamber 128 and thus the carbonized fueland ashes may be withdrawn from the bottom of the shaft without allowinggas to escape. To assist in moving the m carbonized fuel through thehopper 120 a series of pokers 136 pass through the chamher 128 and thehopper 120, by which the carbonized fuel may be barred and broken upwhileit is passing down to the openings 126 of the hopper 120.

An important feature of the present invention consists in giving a highdegree of preheat to the mixture of air and steam bemg used for makinggas whereby the inert material from the combustion of air may beretained in the gas while making a gas of comparatively high calorificvalue and high flame propagation. By preheating the steam and air thegas can be made with a lower percentage of air in proportion to theamount of steam used, and thus cut down the amount of inerts in the gas.This may be demonstrated as follows:

In the exothermic reaction between carbon and air when both the carbonand the. air

start cold, the following reaction takes place:

' CD 3.7 8N 14600 B. T. U.

If, however, the air is preheated to 2000 F.

C+2H O=CO +2H 17400 B. T. U.

4 If however, the steam is preheated to 2000 F. and the carbon isheatedto 1500 F., a gain of approximately 4125 B. U. may be made.

The endothermicreaction between carbon and carbondioxide, assuming thatboth are cold, is substantially as follows C+ CO2=2CO5900 B. T. U.

If, however, the CO is preheated to 2000 F.

and the carbon is preheated to 1500 F. a gain of substantially 2725 B.T. U. may be effected. Assuming that the above reactions take place whenthe constituents are cold, as out lined above, a thermal heat balancemay be obtained when the endothermic reaction between carbon and watervapor and the carbon and carbon dioxide constitutes 45% of the reaction,and the exothermic reaction between 5 carbon and air constitutes 54.5%of the reaction. With such a combustion the analysis of the gas wouldbe, in percentages by volume:

C0 =252 I-I =22.8 N =52.0 B. T. U. value of gas per cubic foot=7 5However, when assuming that the reactions take place, when the steam andair are heated to2000 F. and the carbon is heated to 1500 F. a thermalheat balance will take place when 39% of the constituents enter intoexothermic reactions, and 61% of the constituents enter into anendothermic reaction. Using the heat balance for the preheatedmaterials, a gas formed by the combustion will analyze in percentages byvolume:

(lO =27.2 H =33.1 N =39.7 B. T. U. value of gas per cubic foot=108 Inother words, by preheating the steam, air and carbon. the nitrogencontent is reduced from 52 to 39.7%, the inerts are reduced from 77.2 to66.9% and the calorific values increased from 74.5 to 108 B. T. U. percubic foot. In the present process the degree of preheat dependsstrictly upon the nature of the coal which is being treated, and,preferably, will vary from 1200 F. to 2200 F. By preheating, a gashaving a calorific value of from 200 to 225 B. T. U. per cubic foot maybe produced which has most of the advantageous features of Water gas.The products of combustion of this gas will have a calorific valueranging from -90 B. T. U. per cubic foot even when no preheat isimparted to the blast air.

A typical analysis of a gas made by the present process is substantiallyas follows:

oo.=7%; N =40%; C0='24%; H =25%; CH =4% In accordance with the characterof the coal being treated a gas may be made which will have a totalamount of inerts of from 45 to 52 per cent. Furthermore, by the lowtemperature carbonization applicant is able to gain a substantial amountin volume of methane produced and also gains considerably in the amountof carbon monoxide and hydrogen produced which aid to increase the flametemperature and the flame propagation of the gas. The gas formed incarbonizing the coal above the blast zone has a comparatively high heatvalue, and when this gas is blended with the gas taken ofi through theoff-take 20, a gas is produced which when burned has a flame temperatureranging from 3000 F. 3200 F. and which is therefore suitable forpractically all industrial heating purposes.

With the process outlined above, it will be seen that the manufacture ofgas may be thoroughly controlled, and that the process will give a verygood heat balance because the fuel is introduced and removed from thegenerator substantially cold, and the residual umn through a generator,continuously introducing a blast mixture of steam-and air into amid-portion of the column to maintain gasmaking temperatures therein,passing a portion of the gas-formed upwardly through the fuel above themid-zone to carbonize the fuel by heat transfer therewith and separatelyremoving this enriched producer gas from the top of the generator,removing the major portion of the gas from the generator at a posi- Iducer gas, comprlsmg continuously passing tion directly adjacent themid-portion of the column, introducing water only into the lower portionof the column below themid-zone to cool and quench the fuel, and passingsteam thus generated upwardly through the fuel into the blast zone. v

2. A method of making high quality producer gas, comprising continuouslyintroducing a blast mixture of air and steam into the mid-portion of afuel column'to maintain gas-making temperatures therein, continuouslyexhausting the major portion of the producer gas formed from the centralportion of the fuel column at a position immediately adjacent the blastzone, passing another portion of the producer gas formed through thefuel in the upper portion of the column to dist-i1 said fuel and enrichsaid gas -with its volatile components, continuously introducing a coolstream of water 1nto the lower portion of the column below the blastzoneand passing the steam thus formed upwardly in heat transferringrelationship through the fuel, and preheating the blast mixture byburning the centrally exhausted producer gas in heat interchangingrelationship with the steamand air entering the fuel column.

3. A method of making high quality producer gas, comprising continuouslyblasting a preheated combustion supporting gas, pref- V erably a mixtureof steam and air, Into the mid-portion of a column of fuel to maintaingas-making temperature therein, continuously removing the major portionof the gas formed from the fuel column adjacent the blast zone, passinganother portion of the gas upwardly through the fuel of the column abovethe blast zone to carbonize said fuel,

removing the last mentioned enriched portion of gas from the generatorseparately from the major portion of the gas, and controlling thepreheat imparted to the blast mixtureto produce an enriched gas having agross calorific value of 200 B. T. U, per cubic foot or higher. r

4. A method of making high quality producer gas, comprising continuouslypassing fuel in acolumn through a generator, continuously introducing ablast mixture of steam and air directly into the mid-portion bonize saidfuel by direct heat transfer therewith, removing the last mentionedenriched vportion of gas from the generator separately from the majorportion of gas formed in the blast zone, and cooling and quenching anyunburned carbonized fuel and ash in the column below the blast zone withwater vapor.

5. A method of making high quality profuel in a column through agenerator, continuously introducing a blast mixture of steam and airinto the mid-portion of the fuel column to maintain gas-makingtemperatures therein, passing part of the gas formed upwardly throughthe fuel above the blast zone to carbonize said fuel by diriact heattransfer therewith, preheating said blast mixture to a a degree suchthat an enriched producer gas having a gross calorific value of 200 B.T. U. per cubic foot or higher is produced, and continuously removingsaid enriched gas from the upper part of the generator.

6. A method of making high quality p ro.-

ducer gas, comprising Econtinuously passing fuel in a column through agenerator, continuously introducing a blast mixture of steam and airdirectly into the mid-portion of the column to maintain gas-makingtemperatures therein, preheating said blast mixture to a temperatureabove 1200 F. before tity of air introduced will maintain the amount ofinerts in the gas produced below 52%. Y

7. A method of making producer gas of high calorific value, comprisingcontinuously passing fuel in a column through a genenator, continuouslyintroducing a blast mixture of air and steam peripherally into themid-portion of the fuel column to maintain gas-making temperaturestherein, preheat-, ing said blastmixture before admitting it into thefuel column, removing a part of the gas formed directly from the blastzone of the fuel column,,and passing another portion of the gas formedupwardly through the fuel above the blast zone to carbonize said fueland to enrich said portion of gas with volatile products distilledtherefrom, introducing introducing it into the fuel column, continu- 6enriched producer water into the fuel residue in the lower porrect heattransfer'therewith, passing steam thus formed into the heated blast zoneto generate gas, and continuously removing the gas from the upperportion of the fuel column.

8., A methodof making high quality pro-- ducer gas, comprisingcontinuously passing fuel in a column through a shaft generator,continuously introducing a blast mixture of air and steam into themid-portion of the column around its periphery and forcing the mixturethrough the fuel column to maintain gas-making temperatures therein,exhausting part of the gas formed from the fuel column at a point in itslongitudinal axis directly adjacent the blast zone, passing anotherportion of the gas formed in contact with the fuel in the upper portionof the column to carbonize said fuel and enrich said gas with volatilecomponents distilled therefrom, continuously introducing water into thelower portion of the column to cool and quench the fuel residue therein,and to serve as a medium for returning the sensible heat of the fuel andash passing the blast zone to the midportion of the fuel column.

9. Amethod of making high quality producer gas, which comprises,continuously introducing a, combustion supporting gas, preferably amixture of steam and air, directly 7 into the mid-portion of a column offuel to form a blast zone, and forcing said mixture through thefuelcolumn to maintain gasass'aaae moving from the generator the saidportion of gas, separately removing another portion of the gas formedfrom the fuel column at a pointin the vertical axis thereof adjacent theblast zone, and regenerating and utilizing the potential heat ofwthelast-named portion of gas for generating steam and preheating air forsubsequent use in the process.

In testimony whereof I afiix my signature.

HENRY O. LOBELL.

making temperatures therein, exhausting a portion of gas formed from thefuel at a point in the central portion of the column adjacent the blastzone, passing another portion of the gas formed upwardly in heattransferring relationship through the fuel above the blast zone todistil said fuel and enrich said gas portion with its volatilecomponents, regenerating and utilizing in the process they potentialheat of the centrally exhausted gas and the sensible heat of the fuelresidue and ash in the lower portion of the fuel column, the heat thusregenerated from the centrally exhausted gas being utilized to preheatthe air and to generate and superheat the steam of the air-steam mixtureused in gas making.

' the upper 1200 F. before it enters the column, passing of steam andair mixture to a temperature above a. portion of the gas formed upwardlythrough art of the fuel column in direct contact wit the fuel therein topreheat and carbonize the fuel and enrich-the gas, and re-

